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75 Cards in this Set
- Front
- Back
What is neoglaciation? |
New "ice age" during the holocene era |
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How long ago did neoglaciation occur? |
4500 - 2000 YA |
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What happened to Earth's temperature and glaciers during neoglaciation? |
The global climate cooled Glaciers expanded |
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What did pollen found in Sierran lake sediment cores show? |
Reduced levels of charcoal A shift to trees adapted to cooler climate (fir and pine) |
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How long ago did the bay reach its present size? |
5,000 YA (also earliest evidence of human occupation at this time) |
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What as found in SF shell mounds? |
shells, mud, sand, fish/ bird remains, artifacts, human burials |
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Why is the Bay saltier during a drought? |
There is less river flow entering, so the bay consists of more sea water |
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How much of the Sacramento river flows into the SF bay? |
80% |
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How much of the San Joaquin River flows into the SF bay? |
15% |
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What is an estuary? |
mixture of salt and freshwater |
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Does O16 or O18 evaporate more easily? |
O16 evaporates more easily |
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Does O16 or O18 precipitate more easily? |
O18 precipitates more easily |
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Water enriched in O16 has what level of salinity? |
low salinity levels |
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What can be used to measure Oxygen isotopes to determine past water salinity levels? |
shell chemistry (microfossils/ forminifera) |
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What information does sediment analysis tell us? |
fossil/pollen informaiton, mineralogy/bedding, chemistry of fossil shells, radiocarbon dating |
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Where was Lake Bonneville? |
Utah |
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What remains of Lake Bonneville? |
The Great Salt Lake |
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What can be used as evidence for large ice age lakes? |
Evaporated lake bottom (evaporites) and ancient shorelines |
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Where was Lake Lahontan? |
NW Nevada |
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What caused large ice age lakes to occur? |
Cooler temperatures, so less evaporation and increased precipitation (storms shift downwards due to high sheets of ice |
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What is deglaciation |
thawing of ice |
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What causes deglaciation? |
temperature and CO2 begin rising
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What happens during deglaciation? |
ice sheets begin melting and filling the ocean, sea level rises, large lakes shrink |
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What compound levels tend to correlate with temperature? |
CO2 |
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When did the early Holocene occur? |
10,000 to 7,000 YA |
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What happened during the early Holocene? |
The climate in CA and the west warmed and dried |
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What evidence indicated warmer and drier summers in Sierran lake sediments? |
abundant large charcoal fragments indicated frequent fires, and open forests with oaks replaced dense pine forests |
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When did the "climate optimum" period of global warmth occur? |
Mid Holocene, 7000 to 4500 YA |
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What did CA Bristlecone pines moving upslope indicate? |
warmer climates in CA |
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What do submerged trees indicate? |
prolonged drought caused lake level to drop at one point in time |
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What is an ROV? |
Remotely operated vehicle (deployed to locate submerged tree stumps) |
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Why did people move to the coast during the mid Holocene? |
The coast had more resources |
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Why were there more resources along the coast during the mid holocene? |
Upwelling was strengthened, so cold, nutrient-rich water was brought to the surface -- high nutrient levels lead to high biological productivity (ex. fisheries, shellfish) |
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Why was there an abundance of coastal fog in northern CA? |
Upwelling strengthened, and cold water was brought to the surface. The wind would then blow this cold air to the north |
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When/where did CA water development begin? |
LA, 1900s |
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Where does San Diego get its water from? |
the Colorado river |
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Where does the bay get its water from? |
Mokelumne |
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Where does south bay get its water? |
hetch hetchy |
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Where does LA get its water from? |
LA aqueduct |
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Originally, where did LA get its water? |
the LA river |
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When did LAs population grow too large for its water source (LA river)? |
the early 1900s |
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What is the result of the dried lakebed in the owens valley? |
dust storms and poor air quality |
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What reservoir held water from the owens river? |
St. Francis dam |
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When did the St. Francis Dam burst? |
1928, 600 people died |
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What prompted SF to build another major water project? |
SF earthquake in 1906... fires caused 90% of damage, lacked water supply! |
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Where is hetch hetchy (tuolumne river) valley located? |
yosemite |
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What did the CA aqueduct do? |
transport water from N CA to the central valley and S CA |
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What is eccentricity? |
shape of earth's orbit around the sun, affects amount of solar radiation received on earth |
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How long is an eccentricity cycle? |
100,000 yrs |
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What does the tilt of the earths axis affect? |
the amount of solar radiation received |
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What is precession? |
the wobble of the earth's axis |
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how long is a precession cycle? |
23,000 years |
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How does water temp change during an el nino? |
warmer |
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how does water temp change during a la nina? |
cooler |
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During medieval warm periods, what is more common? |
La Ninas (drier climate in CA and south west) |
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During a little ice age, what is more common? |
el nino, wetter climate in CA and the southwest |
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How long are sunspot cycles? |
11 years, 208, 2300 |
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What happens during a solar max? |
more solar radiation is given off, more sunspots, and more solar energy is received by earth |
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What happens during 2300 yr climate cycles? |
mountain glaciers advance and retreat, and the treeline of bristlecone pines shift up and down |
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How do volcano eruptions affect climate? |
cause cooling |
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What time period had an increase in large volcanic eruptions? |
little ice age |
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How much $$ is the central valley agricultural industry? |
$44 billion |
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How much has the central valley subsided due to groundwater extraction? |
30 ft |
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How much has the temp risen since 1970, what does this mean? |
2F, larger atmospheric river storms and floods |
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Name 2 major periods of global warmth w/ megadroughts: |
middle holocene, midieval warm period |
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Name 2 periods of global cooling w/ wetter climate |
neoglaciation, little ice age |
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When was the little ice age? |
1300 ad |
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Evidence for past megafloods? |
sacramento valley, mono lake, sb basin |
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What are delta layers like in the summer? |
diatom-rich sediments |
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what are delta layers like in the winter? |
land sediments from rains |
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what are delta layers like during large floods? |
thicker layers |
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When was the last megaflood? |
1605 AD |
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What civilization in arizona developed dams and canals? |
hohokam |
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which civilization built pueblos and agriculture? |
anasazi |
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Who built kivas (round ceremonial structures), check dams, canals, and pueblos? |
chaco canyon |